Phosphorylcholine (PC) is a main component of not only an inflammatory phospholipid such as a platelet-activating factor or an oxidized low density lipoprotein but also an immunogenic component of many bacteria including Streptococcus pneumoniae. A compound containing a PC group is used as a PC antigen for the purpose of production of a PC specific antibody. For example, in Patent Literature 1, an example where a PC antigen is used in immunization treatment of atherosclerosis is disclosed. Atherosclerosis is a chronic disease that causes a thickening of the innermost layer (the intima) of large and medium-sized arteries. Atherosclerosis is the major cause of cardiovascular disease including myocardial infarction. Blood flow is decreased in affected areas in atherosclerosis, and ischemia and tissue destruction may be caused in organs supplied by the affected vessel.
According to Patent Literature 1, it is indicated that a monoclonal antibody with specificity to PC and a composition thereof are obtained by using, as a PC antigen, a PC-protein conjugate obtained by boding an immunological carrier protein to PC, and the PC specific monoclonal antibody and the composition thereof are effective in immunization treatment of atherosclerosis. Further, in Patent Literature 2, use of a PC antigen as a vaccine for inducing immunoprotection against infections by Streptococcus pneumoniae or the like is disclosed. Other examples of the study aimed at such a vaccine include Non-Patent Literature 1. In Non-Patent Literature 1, it has been reported that a PC antibody titer is increased by administering a PC-protein conjugate in the presence of an immunopotentiating agent in an animal experiment.
Further, although various methods of introducing a phosphorylcholine group into a molecule to form a polymer complex have been proposed (e.g., Patent Literatures 3 and 4), a PC-protein complex based on a phosphorylcholine group-containing compound has not been developed. This is mainly because a manufacturing process therefor needs a reaction of a plurality of stages and it is not easily manufactured due to the structure for a phosphorylcholine group-containing compound to express its function. Therefore, a PC group-containing compound that is easily manufactured and functions as a PC-protein complex is desired.